Auteurs, date et publication :

Auteurs Tian Zhang , Shu-Lin Bai , Sandrine Bardet , Tancrède Alméras , Bernard Thibaut , Jacques Beauchêne

Publication : Journal of Wood Science

Date : 2011

Volume : 57

Issue : 5

Pages : 377–386

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

Tropical forests have exceptional floristic diversity, but their characterization remains incomplete, in part due to the resource intensity of in-situ assessments. Remote sensing technologies can provide valuable, cost-effective, large-scale insights. This study investigates the combined use of airborne LiDAR and imaging spectroscopy to map tree species at landscape scale in French Guiana. Binary classifiers were developed for each of 20 species using linear discriminant analysis (LDA), regularized discriminant analysis (RDA) and logistic regression (LR). Complementing visible and near infrared (VNIR) spectral bands with short wave infrared (SWIR) bands improved the mean average classification accuracy of the target species from 56.1% to 79.6%. Increasing the number of non-focal species decreased the success rate of target species identification. Classification performance was not significantly affected by impurity rates (confusion between assigned classes) in the non-focal class (up to 5% of bias), provided that an adequate criterion was used for adjusting threshold probability assignment. A limited number of crowns (30 crowns) in each species class was sufficient to retrieve correct labels effectively. Overall canopy area of target species was strongly correlated to their basal area over 118 ha at 1.5 ha resolution, indicating that operational application of the method is a realistic prospect (R2 = 0.75 for six major commercial tree species).

Auteurs, date et publication :

Auteurs Anthony Laybros , Mélaine Aubry-Kientz , Jean-Baptiste Féret , Caroline Bedeau , Olivier Brunaux , Géraldine Derroire , Grégoire Vincent

Publication : Remote Sensing

Date : 2020

Volume : 12

Issue : 10

Pages : 1577

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

Des essais de plantations forestières ont été menés en Guyane française depuis le début des années 1960 sur plus de 138 espèces (70 espèces natives et 68 espèces exotiques). Une étude récente sur la productivité de ces espèces en plantation (projet ForesTreeCulture, 2013-2015) a mis en avant le fort potentiel de production de trois espèces natives (Simarouba amara Aubl., Vochysia tomentosa (G. Mey.) DC., Bagassa guianensis (Aubl.)) et d'une espèce d'Afrique de l'Ouest (Tarrietia utilis Sprague) avec des volumes de bois produits supérieurs à 20 m3/ha/an. Cependant, les propriétés du bois de ces espèces commerciales ne sont connues qu'au travers d'arbres issus de forêt naturelle. Nous présentons les propriétés du bois de ces espèces en conditions de plantation – densité, retrait, élasticité, angle du fil, durabilité – et discutons de leurs potentiels et de leurs usages respectifs futurs. Une autre espèce, Cordia alliodora ((Ruiz et Pavon) Oken), a également été retenue bien qu'elle n'ait pas encore été plantée en Guyane française. Cette espèce, native de Guyane, est bien connue en Amérique latine pour son bois et son fort potentiel de croissance en milieu anthropisé. (Résumé d'auteur)

Auteurs, date et publication :

Auteurs Hélène Morel , Eric-André Nicolini , Julie Bossu , Lilian Blanc , Jacques Beauchêne

Publication : Bois et Forêts des Tropiques

Date : 2025

Volume : 334

Pages : 61–74

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

Forests dominate carbon (C) exchanges between the terrestrial biosphere and the atmosphere on land. In the long term, the net carbon flux between forests and the atmosphere has been significantly impacted by changes in forest cover area and structure due to ecological disturbances and management activities. Current empirical approaches for estimating net ecosystem productivity (NEP) rarely consider forest age as a predictor, which represents variation in physiological processes that can respond differently to environmental drivers, and regrowth following disturbance. Here, we conduct an observational synthesis to empirically determine to what extent climate, soil properties, nitrogen deposition, forest age and management influence the spatial and interannual variability of forest NEP across 126 forest eddy-covariance flux sites worldwide. The empirical models explained up to 62% and 71% of spatio-temporal and across-site variability of annual NEP, respectively. An investigation of model structures revealed that forest age was adominant factor of NEP spatio-temporal variability in both space and time at the global scale as compared to abiotic factors, such as nutrient availability, soil characteristics and climate. These findings emphasize the importance of forest age in quantifying spatio-temporal variation in NEP using empirical approaches.

Auteurs, date et publication :

Auteurs S. Besnard , N. Carvalhais , M. A. Arain , A. Black , S. de Bruin , N. Buchmann , A. Cescatti , J. Q. Chen , Jgpw Clevers , A. R. Desai , C. M. Gough , K. Havrankova , M. Herold , L. Hortnagl , M. Jung , A. Knohl , B. Kruijt , L. Krupkova , B. E. Law , A. Lindroth

Publication : Environmental Research Letters

Date : 2018

Volume : 13

Issue : 12

Catégorie(s)

#CIRAD #FORET CoffeeFlux

Auteurs, date et publication :

Auteurs Y. Nouvellon , J. P. Laclau , D. Epron , G. Le Maire , J. M. Bonnefond , L. M. J. Gonçalves , J. P. Bouillet

Publication : Tree Physiology

Date : 2025

Volume : 00

Pages : 1-16

Catégorie(s)

#CIRAD #FORET Itatinga #INRAE

Auteurs, date et publication :

Auteurs Diarietou Sambakhe , Mathieu Fortin , Jean-Pierre Renaud , Christine Deleuze , Philippe Dreyfus , Nicolas Picard

Publication : Forest Science

Date : 2014

Volume : 60

Issue : 6

Pages : 1050–1059

Catégorie(s)

#CIRAD #FORET Paracou

Résumé

We hypothesized that the nitrogen-fixing tree Acacia mangium could improve the growth and nitrogen nutrition of non-fixing tree species such as Eucalyptus. We measured the N-mineralization and respiration rates of soils sampled from plots covered with Acacia, Eucalyptus or native vegetation at two tropical sites (Itatinga in Brazil and Kissoko in the Congo) in the laboratory. We used a bioassay to assess N bioavailability to eucalypt seedlings grown with and without chemical fertilization for at least 6 months. At each site, Eucalyptus seedling growth and N bioavailability followed the same trends as the N-mineralization rates in soil samples. However, despite lower soil N-mineralization rates under Acacia in the Congo than in Brazil, Eucalyptus seedling growth and N bioavailability were much greater in the Congo, indicating that bioassays in pots are more accurate than N-mineralization rates when predicting the growth of eucalypt seedlings. Hence, in the Congo, planting Acacia mangium could be an attractive option to maintain the growth and N bioavailability of the non-fixing species Eucalyptus while decreasing chemical fertilization. Plant bioassays could help determine if the introduction of N-2-fixing trees will improve the growth and mineral nutrition of non-fixing tree species in tropical planted forests.

Auteurs, date et publication :

Auteurs Kittima Waithaisong , Agnes Robin , Louis Mareschal , Jean-Pierre Bouillet , Jean-Michel Harmand , Bruno Bordron , Jean-Paul Laclau , Jose Leonardo Moraes Goncalves , Claude Plassard

Publication : PLANTS-BASEL

Date : 2023

Volume : 12

Issue : 4

Catégorie(s)

#ANR-Citation #CIRAD #FORET Itatinga

Résumé

Synthetic Aperture Radar (SAR) texture has been demonstrated to have the potential to improve forest biomass estimation using backscatter. However, forests are 3D objects with a vertical structure. The strong penetration of SAR signals means that each pixel contains the contributions of all the scatterers inside the forest canopy, especially for the P-band. Consequently, the traditional texture derived from SAR images is affected by forest vertical heterogeneity, although the influence on texture-based biomass estimation has not yet been explicitly explored. To separate and explore the influence of forest vertical heterogeneity, we introduced the SAR tomography technique into the traditional texture analysis, aiming to explore whether TomoSAR could improve the performance of texture-based aboveground biomass (AGB) estimation and whether texture plus tomographic backscatter could further improve the TomoSAR-based AGB estimation. Based on the P-band TomoSAR dataset from TropiSAR 2009 at two different sites, the results show that ground backscatter variance dominated the texture features of the original SAR image and reduced the biomass estimation accuracy. The texture from upper vegetation layers presented a stronger correlation with forest biomass. Texture successfully improved tomographic backscatter-based biomass estimation, and the texture from upper vegetation layers made AGB models much more transferable between different sites. In addition, the correlation between texture indices varied greatly among different tomographic heights. The texture from the 10 to 30 m layers was able to provide more independent information than the other layers and the original images, which helped to improve the backscatter-based AGB estimation.

Auteurs, date et publication :

Auteurs Zhanmang Liao , Binbin He , Xingwen Quan

Publication : International Journal of Applied Earth Observation and Geoinformation

Date : 2020

Volume : 88

Pages : 102049

Catégorie(s)

#CIRAD #CNRS #FORET Nouragues #FORET Paracou

Résumé

Climate change is expected to increase the frequency of droughts in most tropical regions in the coming decades. A passive phenomenon called hydraulic redistribution (HR) allows some plant species to take up water from deep and wet soil layers and redistribute it in the upper dry layers where other plants and soil biota can benefit from it. In addition, soil fertilization, particularly potassium (K), may also affect drought-adaptive mechanisms and increase water use efficiency (WUE) on poor and acidic tropical soils. The present study aimed at quantifying the role of HR and K fertilization on both wood productivity and WUE for stemwood production (WUEp) of Eucalyptus grandis plantations in Brazil under ambient and reduced (-37%) throughfall conditions. Tree transpiration was measured using trunk sap flow sensors over 21 months, and HR was estimated from the reverse sap flow (RF) observed in shallow roots over 18 months. Tree biomass, hydraulic conductance, soil water storage from surface to the water table (down to 17 m), and leaf photosynthetic capacity were also assessed. Significant HR was detected over the whole year, even during the rainy seasons. Neither potassium fertilization nor throughfall exclusion affected the velocity of water transported by HR, probably because most trees reached water table. Nonetheless, some photosynthetic capacity parameters, including the maximum photosynthetic rate (A(max)), increased in treatments with K addition. This higher A(max) combined with an increased sapwood area index, was associated with an increase in water uptake by 30 %-50 % and WUEp by 300% relative to K-deficient trees. We postulate that the increase in WUEp promoted by potassium fertilization was partly driven by an increase in biomass allocation to wood, at the expense of foraging organs (leaves and roots), because K addition alleviated constraints on light and water use. Our results indicate that fertilizing E. grandis plantations with K is beneficial to both wood biomass production and WUEp.

Auteurs, date et publication :

Auteurs Veronica Asensio , Jean-Christophe Domec , Yann Nouvellon , Jean-Paul Laclau , Jean-Pierre Bouillet , Lionel Jordan-Meille , Jose Lavres , Juan Delgado Rojas , Joannes Guillemot , Cassio H. Abreu-Junior

Publication : ENVIRONMENTAL AND EXPERIMENTAL BOTANY

Date : 2020

Volume : 176

Catégorie(s)

#ANR-Citation #CIRAD #FORET Itatinga

Auteurs, date et publication :

Auteurs P. Battie Laclau , Delgado-Rojas J-S , Christina M , Nouvellon Y , Bouillet J-P , De Cassia Piccolo M , Moreira Marcelo Z , De Moraes Gonçalves J-L , Roupsard O , J.-P. Laclau

Publication : Forest Ecology and Management,

Date : 2025

Volume : 364

Pages : 77-89

Catégorie(s)

#CIRAD #FORET Itatinga #INRAE